Multimedia playing devices are rapidly being miniaturized for portability. For example, mobile communication terminals having a multimedia playing function are equipped with a high-quality display device. Moreover, miniaturization of each component related to a display function becomes a very important factor. There are various kinds of display products using a cathode ray tube (CRT), a liquid crystal display (LCD) device, a light emitting diode (LED), a field emission display (FED), an organic light emitting diode (OLED), etc.
A display module such as an LCD device requires LEDs for backlight and a device for driving the LEDs. Additionally, an interface circuit is provided between the device and control module to deliver a control signal of a control module into the device.
Since the interface circuit is controlled by three kinds of input signals, control operations of the control module are complex and the number of control pins is required according to the number of signals.
Accordingly, since the structure of the interface becomes more complex and larger, it is hard to reduce the size of a multimedia playing device, and also manufacturing cost increases.
FIG. 1 is a waveform diagram of a related art three-line interface.
As illustrated in FIG. 1, a three-line interface apparatus utilizes an enable EN signal, a serial clock SCK, and a serial data SDA signal.
This three-line interface apparatus can be realized with a chip. When eight SCKs are inputted into the three-line interface apparatus according to a predetermined signal input standard, data of SDA is analyzed in rising edges of each SCK to drive six LEDs constituting two groups.
Parameters used in digital signals will be defined in a following Table 1.
TABLE 1ParameterSymbolSCK clock cycletSCKSCK high-level pulse widthtWHSCK low-level pulse widthtWLEN setup timetCSEN hold timetCHEN recovery timetCRWrite data setup timetDSWrite data hold timetDH
The EN signal has two signal states where a high level is a signal enabling an interface of an interface apparatus and a low level is a signal disabling an interface of an interface apparatus.
A voltage of when the EN signal is in a high level is generally in a TTL level. Although an input signal is applied to the interface apparatus, the interface apparatus stops data analysis operations when the EN signal is in a low level. Accordingly, when the EN signal is in a high level, output can be obtained according to an input signal.
SCK represents a data input period. Data of SDA is analyzed in rising edges of the SCKs. The SDA represents an inputted data signal. While the EN signal is inputted in a high level, a signal state is detected in rising edges of SCK signals.
In a related art three-line interface apparatus, since a driving state is controlled by three input lines that is divided according to the kinds of input signals, operational principle is complex, operations takes a long time, and the chip size increases.